This is a revised request for $500,000 towards the purchase of a four channel Varian 600 MHz Inova NMR spectrometer, with a 39 channel Resonance Research Inc shim set and a Nalorac 5mm quadrupole resonance (1H/13C/13N/31P( probe. The higher field strength will give the resolution required for study of proteins greater than or equal to 20 kDa and for RNA: protein complexes (greater than or equal to 18 kDa). Four channels, including deuterium, will make it possible to perform quadruple resonance experiments with predeuterated proteins, as well as use 1H/13C/15N/31P nuclei in RNA applications. In addition, a 19F/1H cryoprobe is requested for the existing 500 MHz instrument, to measure real-time protein folding observed by 19 F-tyrosine or 19F-tryptophan instrument, to measure real-time protein folding observed by 19F- tyrosine or 19F-tryptophan. Acquisition of a 600 MHz instrument will give the sensitivity and resolution required for the larger systems, in addition to providing another field strength necessary for relaxation experiments, and simply giving desperately needed machine time. The cryoprobe allows rapid collection of NMR spectra during the course of a protein (unfolding). Research Projects and training. Four laboratory groups from two departments in the Medical School comprise an NMR research group with collaborations that extend from the Structural Biology Core of the Digestive Diseases Research Core Center at the Medical School, to the Danforth Planet Biology Institute (Monsanto/Washington University). Each group uses NMR to determine protein structure and to observe binding of ligands, including RNA (Kathleen Hall), lipids (David Cistola), and retinoic acid (Ellen Li) and small enzyme co-factors (Carl Frieden), Protein and RNA dynamics are also central to these investigations, using either 15N (proteins) or 13C (RNA) relaxation to characterize the motions of a system.